Photos taken by the craft show guns and gun mounts on the ship, which rested 18,000 feet below the surface. The converted battleship saw action during the Second Sino-Japanese War, the attack on Pearl Harbor, the invasion of Rabaul, and the attack on Darwin, Australia.

The Battle of Midway took place in the Pacific Ocean, near Midway Atoll, on June 4–7, 1942. The battle was an ambush that U.S. forces sprang on Japanese forces in part because U.S. codebreakers had cracked the Japanese secret communication code and knew the whereabouts of large numbers of Japanese forces. During the battle, U.S. forces sunk all four carriers–the Akagi, the Hiryu, the Kaga, and the Soryu–, as well as the Mikuma, a heavy cruiser. Japanese forces sunk one U.S. aircraft carrier, the Yorktown. In total, more than 3,300 servicemen on both sides lost their lives in the battle.

It was yet another high-profile discovery for the research vessel and its team, bankrolled initially by the late Microsoft co-founder Paul Allen. Other recent finds:

• In February 2019, they found the wreck of the U.S. aircraft carrier the USS Hornet, which also took part in the Battle of Midway and, in addition, launched the Doolittle Raid, which rained down bombs on Tokyo in April 1942, providing a much-needed morale boost for the U.S. armed forces in the wake of the attack on Pearl Harbor in late 1941
• In March 2018, they found the remains of the USS Lexington, one of America's first aircraft carriers, sunk during the Battle of the Coral Sea
• Two weeks later, the Petrel and crew found the wreck of the USS Juneau, perhaps most well-known for carrying five brothers from the same family, the Sullivan family from Waterloo, Iowa. The Juneau saw action in the Battle of Santa Cruz Island
• In April 2017, the Petrel and crew found the wreck of the USS Indianapolis, sunk in July 1945, near the end of the war.